Various processes have been known and utilized in the prior art for the separation of gas mixtures into their dominant constituents. Additionally, the use of a single pressure distillation column is known to have been used in the prior art for such separations.
In U.S. Pat. No. 3,214,926 a method for producing liquid oxygen or liquid nitrogen is set forth. However, in the patent it is necessary to have two distillation columns, one at high pressure and another at low pressure in order to extract liquid oxygen.
In U.S. Pat. No. 3,217,502 a system is descrbed which utilizes a single pressure distillation column. The product of this air separation system is liquid nitrogen and the oxygen. which was contained in the air feed, is vented to waste. In this patent, it is the oxygen stream which is expanded in order to provide refrigeration for the air separation system.
An air separation unit for the production of oxygen is disclosed in U.S. Pat. No. 3,394,555 wherein the combustion of a separate fuel source such as powdered coal is burned with oxygen or an air-oxygen mixture in which the oxygen is derived from the air separation unit. This combustion process provided power for the compression of helium gas for refrigeration necessary to the cryogenic separation system. Power from such combustion is derived from a magnetohydrodynamic power generator.
U.S. Pat. No. 3,731,495 discloses an air separation system using an air feed compressor which is powered by combustion gases directed through a turbine. The turbine exhaust heats boiler steam to supplement the compressor drive. Electric generation is also considered. In addition, this reference utilizes two separate columns at separate pressures for the recovery of the individual gaseous components of air which are separated.
U.S. Pat. No. 4,152,130 discloses an air separation unit which has multiple feeds to a two pressure-two stage distillation column. Both feeds to the distillation column are expanded through an expander. The system may produce liquid oxygen or liquid nitrogen as desired.
U.S. Pat. No. 4,224,045 is directed towards a process where oxygen is produced by distillation of liquefied air in a two column unit. A gas turbine, powered in part by a nitrogen stream from the distillation, supplies the energy to compress the feed air.
U.S. Pat. No. 4,382,366 discloses an air separation unit which uses a single pressure distillation column and burns a depleted oxygen stream to provide power for the air compressor, however the oxygen product needs to be recompressed. The distillation column of this patent has a split feed and utilizes a portion of the feed to control reboil and reflux. Reflux control is by introduction of the stream into the top of the column rather than use as a condenser working fluid.
The art as represented above has failed to disclose an efficient manner in which to separate gas constituents from gas mixtures with the utilization of a single pressure distillation column which utilizes the feed gas as the working fluid to provide both reflux and reboil.